Surfactant and method of manufacturing an electrowetting display device using the same

ABSTRACT

A surfactant includes a hydrophobic functional group, a hydrophilic functional group and a linker disposed between the hydrophobic functional group and the hydrophilic functional group, and the linker is connected to the hydrophobic functional group and the hydrophilic functional group. The linker has a cleavable bond with a bond energy lower than a bond energy of a bond included in the hydrophilic functional group and a bond included in the hydrophobic functional group.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority under 35 U.S.C. §119 to KoreanPatent Application No. 10-2011-0090020, filed on Sep. 6, 2011, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

TECHNICAL FIELD

The present disclosure relates to a surfactant, and more particularly,to a surfactant and a method of manufacturing an electrowetting displaydevice using the surfactant.

DISCUSSION OF THE RELATED ART

An electrowetting display device is a display device using anelectrowetting effect.

The electrowetting effect refers to an effect in which a contact anglebetween a conductive hydrophobic fluid and a hydrophobic film disposedunder the fluid changes according to the change in a voltage applied tothe fluid. Specifically, the smaller the voltage applied to thehydrophobic fluid, the smaller the contact angle between the hydrophobicfluid and the hydrophobic film. Further, the smaller the contact angle,the larger the area of the hydrophobic fluid distributed on thehydrophobic film.

An Electrolyte Level Rising (ELR) technology has been proposed whichraises the level of an electrolyte (hydrophilic fluid) disposed in acontainer to distribute the hydrophilic fluid and a hydrophobic fluidover an entire hydrophobic film between a first substrate and a secondsubstrate of an electrowetting display device. The ELR technology has aprocess including, for example, the steps of: slantly immersing a firstsubstrate having a hydrophobic film in an electrolyte (hydrophilicfluid) disposed in a container so that the first substrate is inclinedwith respect to a surface of the fluid, providing a hydrophobic fluidunmixable with the hydrophilic fluid to an area at which the surface ofthe hydrophilic fluid and the hydrophobic film of the substrate are incontact with each other and raising the height (or level) of the surfaceof the hydrophilic fluid in the container to distribute the hydrophilicfluid and the hydrophobic fluid over the entire hydrophobic film.However, the ELR technology may require complicated equipment forapplying the technology and may also have difficulties in reducing theprocessing time and in uniformly distributing the fluids on thesubstrate. Therefore, there may be a need in the art for a manufacturingmethod which enables the hydrophilic fluid and the hydrophobic fluid tobe uniformly distributed on the substrate in a relatively short periodof time. Further, there may also be a need in the art for amanufacturing method which requires a relatively simple manufacturingequipment and a low manufacturing cost.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a way tomanufacture an electrowetting display device by using simple equipment.

Exemplary embodiments of the present invention provide a way tomanufacture an electrowetting display device at a low cost.

Exemplary embodiments of the present invention provide a way tomanufacture an electrowetting display device in short working time.

Exemplary embodiments of the present invention provide a way tomanufacture an electrowetting display device in which a hydrophobicfluid is uniformly distributed on a substrate.

In accordance with an exemplary embodiment of the present invention, asurfactant is provided. The surfactant includes a hydrophobic functionalgroup, a hydrophilic functional group and a linker disposed between thehydrophobic functional group and the hydrophilic functional group, andthe linker is connected to the hydrophobic functional group and thehydrophilic functional group. In addition, the linker has a cleavablebond with a bond energy lower than a bond energy of a bond included inthe hydrophilic functional group and a bond included in the hydrophobicfunctional group.

The hydrophobic functional group has a structure dissolvable byhydrophobic fluid molecules, and the hydrophilic functional group has astructure dissolvable by hydrophilic fluid molecules of. The hydrophobicfunctional group and the hydrophilic functional group include one of acarbon-carbon bond or a carbon-oxygen bond, the cleavable bond has abond energy lower than a bond energy of the carbon-carbon bond or a bondenergy of the carbon-oxygen bond included in the hydrophobic functionalgroup and the hydrophilic functional group, and the cleavable bond isconfigured to be broken by absorbing an energy of no less than the bondenergy of the carbon-carbon bond or bond energy of the carbon-oxygenbond included in the hydrophobic functional group and the hydrophilicfunctional group.

The cleavable bond has a bond energy which is no greater than about 600kJ/mol.

The cleavable bond may have a bond selected from the group consisting ofa carbon-silicon (C—Si) bond, a carbon-phosphor (C—P) bond, anitrogen-silicon (N—Si) bond, a nitrogen-sulfur (N—S) bond, anoxygen-oxygen (O—O) bond, an oxygen-sulfur (O—S) bond, a sulfur-phosphor(S—P) bond, a sulfur-sulfur (S—S) bond, and combinations thereof.

The hydrophobic functional group may be a functional group of ahydrocarbon having ten or more carbons, the hydrophilic functional groupmay include an ether functional group, and the cleavable bond may be asulfur-sulfur (S—S) bond.

The surfactant may be a 2-[(Methoxyethoxy)ethoxy]ethyl decyl disulfide.

The surfactant may be manufactured from an alcohol, which is the firststarting material, and a thiol, which is the second starting material.

The hydrophobic functional group may be an alkane functional grouphaving ten or more carbons.

The cleavable bond of the surfactant may have a bond selected from thegroup consisting of a carbon-silicon (C—Si) bond, a carbon-phosphor(C—P) bond, a nitrogen-silicon (N—Si) bond, a nitrogen-sulfur (N—S)bond, an oxygen-oxygen (O—O) bond, an oxygen-sulfur (O—S) bond, asulfur-phosphor (S—P) bond, a sulfur-sulfur (S—S) bond, and combinationsthereof.

The hydrophilic functional group may include an ether bond.

The cleavable bond may be broken by an energy supplied from an outsideof the surfactant and the energy may be provided by ultraviolet rays,heat, or a combination thereof.

The cleavable bond may be broken by an energy lower than bond energiesof bonds included in the hydrophobic functional groups and bondsincluded in the hydrophilic functional groups.

In accordance with an exemplary embodiment of the present invention, anelectrowetting display device is provided. The electrowetting displaydevice includes a first substrate, a pixel electrode disposed on thefirst substrate, a hydrophobic film disposed on the pixel electrode, ahydrophobic fluid disposed on an area of the hydrophobic film, and thearea on which the hydrophobic fluid is configured to move on thehydrophobic film in response to a voltage applied to the pixelelectrode, a hydrophilic fluid disposed on the hydrophobic fluid and asecond substrate disposed on the hydrophilic fluid and spaced apart fromthe hydrophobic film. The hydrophobic fluid includes molecules includinghydrophobic functional groups of a cleavable surfactant and thehydrophilic fluid includes molecules including hydrophilic functionalgroups of the cleavable surfactant.

The surfactant includes a hydrophobic functional group, a hydrophilicfunctional group, and a linker interconnecting the hydrophobicfunctional group and the hydrophilic functional group. The linker has acleavable bond, and the hydrophobic fluid or the hydrophilic fluid mayinclude an element participating in the cleavable bond.

The cleavable surfactant may have a bond selected from the groupconsisting of a carbon-silicon (C—Si) bond, a carbon-phosphor (C—P)bond, a nitrogen-silicon (N—Si) bond, a nitrogen-sulfur (N—S) bond, anoxygen-oxygen (O—O) bond, an oxygen-sulfur (O—S) bond, a sulfur-phosphor(S—P) bond, a sulfur-sulfur (S—S) bond, and combinations thereof.

The cleavable bond may be a sulfur-sulfur (S—S) bond and the hydrophobicfluid or the hydrophilic fluid may include thiol molecules.

The hydrophobic fluid may include a saturated hydrocarbon having atleast ten carbon atoms, the hydrophilic fluid may include ethyleneglycol and glycerin, the hydrophobic functional group may be afunctional group of a hydrocarbon having ten or more carbons, and thehydrophilic functional group may include a functional group including anether bond.

The surfactant may further include a linker interconnecting thehydrophobic functional group and the hydrophilic functional group, andthe linker may have a cleavable bond selected from the group consistingof a carbon-silicon (C—Si) bond, a carbon-phosphor (C—P) bond, anitrogen-silicon (N—Si) bond, a nitrogen-sulfur (N—S) bond, anoxygen-oxygen (O—O) bond, an oxygen-sulfur (O—S) bond, a sulfur-phosphor(S—P) bond, a sulfur-sulfur (S—S) bond, and combinations thereof.

The cleavable bond may be a sulfur-sulfur (S—S) bond and the hydrophobicfluid or the hydrophilic fluid may include thiol molecules.

In accordance with an exemplary embodiment of the present invention, amethod of manufacturing an electrowetting display device is provided.The method includes providing a first substrate including a first basesubstrate having a plurality of pixel electrodes formed on the firstbase substrate, a hydrophobic film formed on the plurality of pixelelectrodes, and at least one sealing member formed at an edge of thefirst substrate, mixing a hydrophobic fluid, a hydrophilic fluid, and acleavable surfactant with each other to form an emulsion, wherein thecleavable surfactant includes a hydrophobic functional group, ahydrophilic functional group and a linker disposed between thehydrophobic functional group and the hydrophilic functional group, andwherein the linker is connected to the hydrophobic functional group andthe hydrophilic functional group. The linker has a cleavable bond with abond energy lower than a bond energy of a bond included in thehydrophilic functional group and a bond included in the hydrophobicfunctional group. The method further includes applying the emulsion onthe first substrate, applying at least one of ultraviolet rays or heaton the emulsion applied on the first substrate to separate thehydrophobic fluid and the hydrophilic fluid from each other anddisposing a second substrate on the sealing members of the firstsubstrate.

A substantially identical amount of hydrophobic fluid may be distributedin each of the pixel electrodes.

A width of a pixel disposed on the first substrate in an area in whichthe emulsion is disposed may be greater than a width of a pixel disposedon another area of the first substrate in which the emulsion is notdisposed. The emulsion may be dispensed onto the first substrate througha nozzle of a dispenser as a droplet, the emulsion droplet may havewidth in a direction parallel to the first substrate before the emulsionis dropped onto the substrate after being discharged out of the nozzle,and the with of at least one of the pixels disposed on the firstsubstrate may be smaller than the width of the emulsion droplet.

The emulsion droplet becomes a dispensed emulsion when the emulsiondroplet has been dispensed onto the first substrate, and the dispensedemulsion may have a width greater than the width of at least one of thepixels disposed on the first substrate.

The width of the dispensed emulsion may not be greater than ten timesthe width of at least one of the pixels disposed on the first substrate.

The emulsion may be dispensed onto the first substrate after becoming anemulsion droplet formed by the nozzle of the dispenser, the emulsiondroplet becomes a dispensed emulsion when the emulsion droplet has beendispensed onto the first substrate, and one dispensed emulsion mayoverlap an adjacent dispensed emulsion.

The emulsion may be formed by mixing the hydrophobic fluid, thehydrophilic fluid, and the cleavable surfactant within a container.

The cleavable surfactant may include a hydrophobic functional group, ahydrophilic functional group, and a linker interconnecting thehydrophobic functional group and the hydrophilic functional group andhaving a cleavable bond, and the at least one of the ultraviolet rays orheat applied on the emulsion may have an intensity capable of breakingthe cleavable bond earlier than bonds of the hydrophilic functionalgroup and the hydrophobic functional group.

In accordance with an exemplary embodiment of the present invention, amethod of manufacturing an electrowetting display device is provided.The method includes providing a first substrate including a first basesubstrate having a plurality of pixel electrodes formed on the firstbase substrate and a hydrophobic film formed on the plurality of pixelelectrodes, mixing a hydrophobic fluid, a hydrophilic fluid, and asurfactant having a linker with each other to form an emulsion includinga micelle in which a hydrophobic functional group of the surfactant isbonded to a molecule of the hydrophobic fluid, a hydrophilic functionalgroup of the surfactant is bonded to a hydrophilic molecule of thehydrophilic fluid, and the linker of the surfactant has a cleavable bondthat interconnects the hydrophobic functional group and the hydrophilicfunctional group to each other, wherein the hydrophobic functional groupand the hydrophilic functional group include at least one of acarbon-carbon bond or a carbon-oxygen bond. The cleavable bond has abond energy lower than a bond energy of the at least one of acarbon-carbon bond or a carbon-oxygen bond included in the hydrophobicfunctional group and the hydrophilic functional group.

In addition, the method further includes applying the emulsion on thefirst substrate, applying a form of energy to the emulsion to break thecleavable bond of the linker of the surfactant and to separate thehydrophobic fluid and the hydrophilic fluid from each other such thatthe separated hydrophobic fluid and the separated hydrophilic fluid areunmixable with each other and disposing a second substrate on the firstsubstrate.

By using the separable surfactants according to exemplary embodiments ofthe present invention, it is possible to uniformly distribute thehydrophobic fluid over the entire display device. Further, it ispossible to manufacture an electrowetting display device by simplemanufacturing facilities, with low manufacturing costs, and in a shortmanufacturing time.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention can be understood in moredetail from the following detailed description taken in conjunction withthe accompanying drawings, in which:

FIGS. 1A and 1B are rough enlarged sectional views of one pixel of anelectrowetting display device;

FIG. 2 is an enlarged schematic diagram illustrating a micelle formed byhydrophobic fluid molecules and hydrophilic fluid molecules andsurfactant molecules according to an exemplary embodiment of the presentinvention;

FIG. 3 illustrates a Table showing bond energies of main bonds includedin organic compounds;

FIGS. 4A to 4F are photographs showing the states in which a surfactantis mixed with a hydrophobic fluid and a hydrophilic fluid so as to forman emulsion;

FIGS. 5A and 5B are a Gas Chromatography-Mass Spectroscopy (GC-MS) graphshowing measured surfactant components dissolved by ultra-violet raysand a table showing the information of detected materials, respectively;and

FIGS. 6A to 6F are rough sectional views of a substrate and a fluidmixer for a process of injecting an emulsion into an electrowettingdisplay device and then converting the emulsion into hydrophilic andhydrophobic fluids according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription, the same elements will be designated by the same referencenumerals although they are shown in different drawings. Further, variousspecific definitions found in the following description, such asspecific numeral values are provided only to help general understandingof exemplary embodiments of the present invention, and it is apparent tothose skilled in the art that exemplary embodiments of the presentinvention can be implemented without such definitions.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present.

As used herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

FIGS. 1A and 1B are rough enlarged sectional views of one pixel of anelectrowetting display device. The electrowetting display device 1includes, for example, a first substrate 100, a hydrophobic fluid 210disposed on the first substrate 100, a hydrophilic fluid 230 disposed onthe hydrophobic fluid 210 and unmixable with the hydrophobic fluid 210,and a second substrate 190. The hydrophobic fluid 210 and thehydrophilic fluid 230 are interposed between the first substrate 100 andthe second substrate 190. The first substrate 100 may include, forexample, a first base substrate 110, a pixel electrode 120 formed on thefirst base substrate 110, and a hydrophobic film 130 formed on the pixelelectrode 120. For example, hydrophobic banks 140 limiting the movementof the hydrophobic fluid 210 are formed on parts of the hydrophobic film130.

The hydrophobic fluid 210 is, for example, a fluid containing a dye of apredetermined color and is distributed over the entire hydrophobic film130 as shown in FIG. 1A when no voltage is applied to the pixelelectrode 120. For example, when the hydrophobic fluid 210 includes ablack dye, the light having entered into the pixel from the exterior ofthe first substrate 100 cannot pass through the hydrophobic fluid 210,and the pixel thus looks black. When a voltage is applied to the pixelelectrode 120, the hydrophobic fluid 210 moves toward the hydrophilicbanks 140 in proportion to the voltage applied to the pixel electrode120 as shown in FIG. 1B. In this event, the area of the blackhydrophobic fluid 210 distributed on the hydrophobic film 130 changesaccording to a change in the value of the voltage applied to the pixelelectrode 120. As the contrast level of the display device 1 is inproportion to an exposed area of the hydrophobic film 130, the displaydevice 1 displays a predetermined image.

The first base substrate 110 and the second substrate 190 may be, forexample, a flexible substrate or a rigid substrate. For example, thefirst base substrate 110 and the second substrate 190 may includeflexible substrates made of glass, plastic, or a glass fiber reinforcedplastic (FRP).

In addition, the pixel electrode 120 may include, for example, atransparent conductive material such as ITO (indium tin oxide), IZO(indium zinc oxide), aluminum zinc oxide (AZO), or cadmium tin oxide(CTO). Alternatively, the pixel electrode 120 may include, for example,a reflective electric conductor such as aluminum (Al), gold (Au), silver(Ag), copper (Cu), iron (Fe), titanium (Ti), tantalum (Ta), molybdenum(Mo), rubidium (Rb), tungsten (W), and alloys, or combinations thereof.

Moreover, the hydrophobic film 130 may include, for example, amorphousfluoropolymers such as copolymers of tetrafluoroethylene (TFE) andperfluro-2,2 dimethyl 1,3 dioxide (PDD), sold under the brand nameTEFLON® AF 1600 which is a registered trademark of the E.I. DuPont deNemours and Company Corporation, 101 West 10th St., Wilmington, Del.19898). Alternatively, other low surface energy polymers such as, forexample, parylene may be used to form the hydrophobic film.

The hydrophilic banks 140 may include, for example, a positivephotoresist, a negative photoresist, a photoset resin or a thermosetresin.

For example, according to characteristics of exemplary embodiments ofthe present invention, a hydrophobic fluid 210 and a hydrophilic fluid230, which are originally not mixed with each other, are mixed with eachother to become an emulsion by a surfactant. A molecule of thesurfactant is expressed by, for example, a general formulaR(Pho)-L-R(Phi), which includes a hydrophobic functional group R(Pho)and a hydrophilic functional group R(Phi) having structures, which canbe mixed well with the hydrophobic fluid 210 and the hydrophilic fluid230, and a linker L, which interconnects the hydrophobic functionalgroup R(Pho) and the hydrophilic functional group R(Phi) to each other.In addition, the linker L has a cleavable bond of a low bond energy. Itis noted that reference characters R(Pho) and 310 are usedinter-changably throughout to refer to the hydrophobic functional groupof the surfactant molecule and reference characters R(Phi) and 320 areused inter-changably throughout to refer to the hydrophilic functionalgroup of the surfactant molecule.

After the emulsion is applied onto a substrate, the cleavable bonds ofthe surfactant molecule included in the emulsion are broken by absorbingan energy, such as, for example, light or heat, and the functionalgroups of the surfactant molecules are then mixed with hydrophobic 210and hydrophilic 230 fluids. Therefore, it is possible to produce anelectrowetting display device including hydrophobic and hydrophilicfluids unmixable with each other.

For example, with regard to the molecules of a surfactant according toan exemplary embodiment of the present invention, hydrophobic functionalgroups R(Pho) of the molecules are dissolved by the molecules of thehydrophobic fluid 210 and hydrophilic functional groups R(Phi) of themolecules are dissolved by the molecules of the hydrophilic fluid 230.Therefore, the molecules of the surfactant may be, for example,simultaneously combined with the molecules of the hydrophobic fluid 210and the hydrophilic fluid 230, so as to form a micelle. FIG. 2 is aschematic diagram illustrating a micelle formed by hydrophobic andhydrophilic fluid molecules and surfactant molecules according to anexemplary embodiment of the present invention. Referring to FIG. 2, amicelle 370 includes, for example, a hydrophobic fluid 210 andsurfactant molecules 300 compactly gathering around the hydrophobicfluid 210. Each surfactant molecule 300 includes, for example, ahydrophobic functional group 310 connected to a molecule of thehydrophobic fluid 210, a hydrophilic functional group 320 connected to amolecule of the hydrophilic fluid 230, and a linker 330 disposed betweenthe hydrophobic functional group 310 and the hydrophilic functionalgroup 320 and interconnecting the hydrophobic functional group 310 andthe hydrophilic functional group 320 to each other.

The hydrophobic functional group 310 has a hydrophobic structure. Forexample, the hydrophobic functional group 310 may have a structureselected from the group consisting of structures of nonpolar straightchain alkyl group, branched-chain alkyl group, branched-chainsubstituted alkyl group, cyclic substituted alkyl group, andcombinations thereof Those alkyl groups described above may be, forexample, a saturated hydrocarbon. Alternatively, for example, in anexemplary embodiment, the alkyl groups described above may be ahydrocarbon including a multiple bond. Also, as an alternative, thehydrophobic functional group 310 may have, for example, a structuresimilar to the structure of the molecules included in the hydrophobicfluid 210. For example, if the hydrophobic fluid 210 includes alkanemolecules, the hydrophobic functional group 310 may be an alkanefunctional group. For example, if the hydrophobic fluid 210 includesdecane molecules, the hydrophobic functional group 310 may be a decanefunctional group or a functional group of another saturated hydrocarbonhaving more than ten carbons. It is also noted that the decane molecule,which is hydrophobic, has a structure in which a black dye formed ofanthraquinone-based molecules can be dissolved well, and simultaneouslyhas a property that it may be unmixable with a fluid in which ethyleneglycol molecules and/or glycerin molecules are mixed.

The hydrophilic functional group 320 has a hydrophilic structure. Forexample, the hydrophilic functional group 320 may have a structureselected from the group consisting of structures of polar hydroxylgroup, carboxyl group, ether group, ester group, amino group, multiplebond of carbon and carbon, and combinations thereof. As an alternative,the hydrophilic functional group 320 may have, for example, a structuresimilar to the structure of molecules included in the hydrophilic fluid230. For example, if the hydrophilic fluid 230 includes ethylene glycolmolecules, the hydrophilic functional group 320 may be an ethyleneglycol functional group. As another alternative, if the hydrophilicfluid 230 includes glycerol molecules, the hydrophilic functional group320 may be, for example, a glycerol functional group. As anotheralternative, if the hydrophilic fluid 230 includes glycerol moleculesand glycerin molecules mixed with each other, the hydrophilic functionalgroup 320 may be, for example, a functional group including a pluralityof ethers. It is noted that the ethylene glycol molecules and theglycerin molecules are connected to neither the hydrophobic fluid 210nor dye or pigment dissolved or dispersed within the hydrophobic fluid230.

It is noted that the structural similarity between the hydrophobicfunctional group 310 and the molecules of the hydrophobic fluid 210 andthe structural similarity between the hydrophilic functional group 320and the molecules of the hydrophilic fluid 230 are beneficial for therespective mixing of the hydrophobic functional group 310 and thehydrophilic functional group 320 with the hydrophobic fluid 210 and thehydrophilic fluid 230 after the step of separating the surfactantmolecules 300 into hydrophobic and hydrophilic molecules by a method ofmanufacturing an electrowetting display device according to the presentexemplary embodiment of the present invention described below.

The present exemplary embodiment discusses black dyes included in thehydrophobic fluid 210 but exemplary embodiments are not limited thereto.For example, alternatively in an exemplary embodiment, the hydrophobicfluid 210 may include other dyes or pigments of primary colors such asred, green, cyan, magenta, blue, or yellow.

The linker 330 is connected to both the hydrophobic functional group 310and the hydrophilic functional group 320, so as to indirectly connectthe functional groups with each other. Further, the linker 330 includes,for example, a cleavable bond in its structure. The cleavable bond ofthe linker 330 is broken, for example, when the linker receives energy,such as heat or light, or reacts with another material additionallyadded thereto. By the breaking of the cleavable bond of the linker 330,the hydrophobic functional group 310 and the hydrophilic functionalgroup 320 connected to the linker 330 are separated from each other, sothat the micelle 370 as shown in FIG. 2 may be broken up. As a resultand as described in further detail in connection with FIG. 6E, theemulsion may be separated into a separated hydrophobic fluid 213 whichincludes the hydrophobic functional group 310 of the surfactant molecule300 mixed with molecules of the hydrophobic fluid 210 and a separatedhydrophilic fluid 233 which includes the hydrophilic functional group320 mixed with molecules of the hydrophilic fluid 230. The separatedhydrophobic fluid 213 and the separated hydrophilic fluid 233 do not mixwith each other.

Surfactant molecules 300 according to an exemplary embodiment of thepresent invention are designed to enable the bond cleavage or bondbreaking to be applied to the linker 330 either selectively or with afirst priority, rather than being applied to the hydrophobic functionalgroup 310 or the hydrophilic functional group 320. When the hydrophobicfunctional group 310 and the hydrophilic functional group 320 include acarbon-carbon (C—C) bond or a carbon-oxygen (C—O) bond, the linker 330should have, for example, a structure including a bond energy lower thanthe bond energy of the C—C bond or the C—O bond.

FIG. 3 illustrates a Table showing bond energies of main bonds includedin organic compounds. Referring to FIG. 3, the bond energies of the C—Cenergy or the C—O bond, which are included much in the hydrophobicfunctional group 310 and the hydrophilic functional group 320 and shouldbe broken as little as possible, are higher than, for example, about 600kJ/mol. Therefore, it is beneficial that the bond energy of thecleavable bond included in the structure of the linker 330 is smallerthan about 600 kJ/mol. For example, as bonds of carbon-silicon (C—Si),carbon-phosphor (C—P), nitrogen-silicon (N—Si), nitrogen-sulfur (N—S),oxygen-oxygen (O—O), oxygen-sulfur (O—S), sulfur-phosphor (S—P), andsulfur-sulfur (S—S) have bond energies which are lower than about 600kJ/mol, they may be included in the structure of the linker 330.

Among the bonds having low bond energies, the S—S bond can be obtainedby, for example, the following reaction formulas set forth below.

The surfactant molecule 300 having an S—S bond as shown in Reactionformula 3 is synthesized from, for example, an alcohol molecule, whichis the first starting material as disclosed in reaction formula 1, and athiol molecule, which is the second starting material as disclosed inReaction formula 2. Referring to Reaction formula 1, a hydrogen atom ofthe alcohol molecule, which is the first starting material and includesa hydrophilic group, is replaced by a tosyl group disclosed in Chemicalformula 1 below, so that the alcohol molecule is converted to an alkylsulfonate molecule as shown in Chemical formula 2. The alkyl sulfonatemolecule is converted to a thiol molecule R(Phi)-SH by, for example, aheating reaction. Referring to Reaction formula 2, the thiol moleculeR(Pho)-SH, which includes a hydrophobic group R(Pho) and is the secondstarting material, is mixed with trimethyl amine molecules and dichloromethane molecules and reacts with 2,2′-Dithiodipyridine molecules tobecome a disulfanyl molecule. Referring to Reaction formula 3, a sulfuratom of the disulfanyl molecule synthesized by Reaction formula 2 isreplaced by a sulfur atom of the thiol molecule synthesized by Reactionformula 1. As a result, a disulfur compound, which is a surfactantmolecule 300 and includes a linker 330 having a covalent bond of a lowbond energy, is synthesized.

For example, a hydrophobic fluid molecule according to an embodiment ofthe present invention is a decane molecule, which corresponds to asaturated hydrocarbon consisting of ten carbons and having a straightchain structure, and a hydrophilic fluid corresponds to a mixture inwhich ethylene glycol molecules and glycerin molecules are mixed by aweight ratio of about 2:1. Therefore, based on the fact that functionalgroups of surfactant molecules 300 are dissolved well when they havestructures similar to those of the molecules of the hydrophobic 210 andhydrophilic fluids 230, the hydrophobic functional group 310 dissolvedin the hydrophobic fluid 210 may be, for example, a hydrocarbonincluding at least ten carbons and the hydrophilic functional group 320dissolved in the hydrophilic fluid 230 may have, for example, astructure in which at least three ethers are connected to each otherthrough carbons between the ethers. Further, based on the fact that thelinker 330 of the surfactant molecules 300 has a bond energy lower thanabout 600 kJ/mol, the surfactant molecules 300 may be a2-[(Methoxyethoxy)ethoxy]ethyl decyl disulfide disclosed in Chemicalformula 3 below. It is noted that the material of Chemical formula 3 canbe synthesized by, for example, Reaction formulas 1 to 3 describedabove.

Experiments of mixing fluids and dissolving a surfactant molecule 300were performed, to examine if a surfactant molecule 300 employing thehydrophobic 310 and hydrophilic 320 functional groups and a linker 330is converted to an emulsion including micelles 370 when they are mixedwith hydrophobic 210 and hydrophilic 230 fluids and if this emulsion isthen converted, by, for example, light or heat, to fluids unmixable witheach other.

FIGS. 4A to 4F are photographs showing the states in which a surfactantis mixed with a hydrophobic fluid 210 and a hydrophilic fluid 230 so asto form an emulsion. In this experiment, surfactant molecules 300including S—S bonds having a low bond energy as shown in Chemicalformula 3 were used, a fluid in which anthraquinone-based black dyemolecules and decane molecules are mixed was used as a hydrophobic fluid210, and a fluid in which ethylene glycol molecules and glycerolmolecules are mixed by a weight ratio of about 2:1 was used as ahydrophilic fluid 230. In the experiment, solutions containingsurfactants of different percentages were used. Each solution containeda hydrophilic fluid 230 and a hydrophobic fluid 210 by a weight ratio ofabout 1:9, and the surfactant occupied about 0 wt %, about 10 wt %, andabout 15 wt % of the solutions, respectively.

Referring to FIGS. 4A to 4F, three containers from the left to the rightin each photograph contain about 0%, about 10%, and about 15% ofsurfactants by weight, respectively. FIGS. 4A to 4F sequentially showthe states of the containers before, directly after, at about fiveminutes after, at about ten minutes after, at about thirty minutesafter, and at about sixty minutes after the fluids are mixed. As notedfrom the figures, the quantity of input surfactant is proportional tothe time during which the solution is maintained in the emulsion state.Therefore, it is possible to conclude that the disulfide described abovehas a function of mixing a hydrophilic fluid 230 and a hydrophobic fluid210 with each other.

According to an exemplary embodiment of the present invention, thecleavable bond included in the linker 330 of the surfactant molecule 300has a strength weaker and is more easily broken than the bonds includedin the hydrophobic 310 and hydrophilic 320 functional groups of thesurfactant molecules 300. To confirm this property, the surfactantmolecules 300 were dissolved and the structure of the dissolved partswere examined. FIGS. 5A and 5B are a Gas Chromatography-MassSpectroscopy (GC-MS) graph showing measured surfactant componentsdissolved by ultra-violet rays and a table showing the information ofdetected materials, respectively. Samples in which methanol and2-[(Methoxyethoxy)ethoxy]ethyl decyl disulfide as disclosed in Chemicalformula 3 were mixed with each other at a mass ratio of about 99:1 wereused in the experiments. Further, ultra-violet rays of about 185 nmhaving an average energy of about 1.318 J/cm² and ultra-violet rays ofabout 245 nm having an average energy of about 8.16 J/cm² were radiatedon samples 1 to 4 for about 0 minutes, about 3 minutes, about 10minutes, and about 15 minutes, respectively.

Referring to FIGS. 5A and 5B, the quantity of surfactant included ineach sample was reduced in proportion to the time during which thesample was exposed to the ultraviolet rays. Instead, 1-decanethiolmolecules were generated while the S—S bonds included in the linkers 330of the surfactant molecules 300 were broken. As the time during whichthe sample was exposed to the ultraviolet rays increased, the1-decanethiol molecules were increasingly dissolved and some of themwere even changed to decane molecules. As the structure of the decanemolecule is equal to the structure of the hydrophobic fluid 210, thedecane molecules should not act as impurities of the electrowettingdisplay device. The radiation of the ultraviolet rays on the surfactantgenerated molecules which included to molecules derived from thehydrophilic functional groups 320 of the surfactant and had a structuresimilar to that of the hydrophilic fluid 230 of the electrowettingdisplay device. Therefore, the decane molecules should not act asimpurities of the electrowetting display device.

Also, in the process of manufacturing the electrowetting display device,if the quantity of the surfactant is very little in comparison with theentire quantity of the hydrophobic fluid 210 or the hydrophilic fluid230, a generation of undesired impurities in which the C—C bond or C—Obond of the surfactant molecules 300 are broken may not influence themovement of the fluids included in the completed electrowetting displaydevice.

It is noted that exemplary embodiments of the present invention are notlimited to using ultraviolet rays to break the cleavable bond includedin the linker 330 of the surfactant molecule 300. For example,alternatively, in an exemplary embodiment, ultraviolet rays and heat maybe simultaneously applied to the surfactant molecule 300 to break thecleavable bond included in the linker 330 of the surfactant molecule300. Moreover, alternatively, for example, in an exemplary embodiment, asound wave energy, such as an ultrasonic wave may be applied to thesurfactant molecule 300 to break the cleavable bond included in thelinker 330 of the surfactant molecule 300.

FIGS. 6A to 6F are rough sectional views of a substrate and a fluidmixer for a process of injecting an emulsion into an electrowettingdisplay device and then converting the emulsion into hydrophilic andhydrophobic fluids according to an exemplary embodiment of the presentinvention. Referring to FIG. 6A, which is a rough sectional view of afirst substrate of an electrowetting display device according to anexemplary embodiment of the present invention, the first substrate 100includes, for example, a first base substrate 110, a pixel electrode120, a hydrophobic film 130, and hydrophilic banks 140 as describedabove with reference to FIGS. 1A and 1B. The first base substrate 110may be, for example, a flexible substrate or a rigid substrate. Forexample, the first base substrate 110 may include flexible substratesmade of glass, plastic, or a glass fiber reinforced plastic (FRP).

In addition, the pixel electrode 120 may include, for example, atransparent conductive material such as ITO (indium tin oxide), IZO(indium zinc oxide), aluminum zinc oxide (AZO), or cadmium tin oxide(CTO). Alternatively, in an embodiment, the pixel electrode 120 mayinclude, for example, a reflective electric conductor such as aluminum(Al), gold (Au), silver (Ag), copper (Cu), iron (Fe), titanium (Ti),tantalum (Ta), molybdenum (Mo), rubidium (Rb), tungsten (W), and alloys,or combinations thereof.

Moreover, the hydrophobic film 130 may include, for example, amorphousfluoropolymers such as copolymers of tetrafluoroethylene (TFE) andperfluro-2,2 dimethyl 1,3 dioxide (PDD), sold under the brand nameTEFLON® AF 1600 which is a registered trademark of the E.I. DuPont deNemours and Company Corporation, 101 West 10th St., Wilmington, Del.19898). Alternatively, other low surface energy polymers such as, forexample, parylene may be used to form the hydrophobic film.

The hydrophilic banks 140 may include, for example, a positivephotoresist, a negative photoresist, a photoset resin or a thermosetresin.

The first substrate 100 further includes, for example, sealing members150, which are disposed at edges of the first substrate 100. The sealingmembers 150 are in contact with a second substrate (not shown), andprevent fluids (not shown) within the display device from leaking out ofthe display device. It is noted that exemplary embodiments of thepresent invention are not limited to the sealing members 150 beingformed at edges of the first substrate 100. Alternatively, for example,in an exemplary embodiment, the sealing members 150 may instead beformed on edges of the second substrate prior to attachment of thesecond substrate to the first substrate 100 and then the emulsion 380described in FIG. 6B may be formed between the attached first substrate100 and the second substrate.

FIG. 6B is a rough sectional view of a fluid mixer 510 in a step inwhich the emulsion is made. For example, in this step, a hydrophobicfluid, a hydrophilic fluid, and a surfactant are input to a container511 and are then mixed by a mixing device 513 to become an emulsion 380.For the uniformity of display and brightness of the electrowettingdisplay device, it is possible to use a smaller quantity of hydrophobicfluid 210, which contains, for example, a dye or a pigment expressingthe color of a pixel, than the hydrophilic fluid 230. For example, it ispossible to use a hydrophobic fluid 210 and a hydrophilic fluid 230 in aweight ratio of about 1:9. As an alternative, it is also possible touse, for example, a larger quantity of hydrophobic fluid 210 than thehydrophilic fluid 230. The surfactant may be input to the fluid mixer510, for example, either simultaneously with or after the hydrophobic210 and hydrophilic 230 fluids. It should be noted that undesiredelements, such as bubbles, may be formed within the container 511 whilethe hydrophobic fluid 210 and the hydrophilic fluid 230 are mixed witheach other and thus the emulsion forming step may include, for example,an additional sub-step, such as a step of defoamation.

FIG. 6C is a rough sectional view of the first substrate shown in FIG.6A in a step in which the emulsion shown in FIG. 6B is dispensed ontothe first substrate 100. For example, a dispenser 520 for dispensing thepreviously produced emulsion 380 onto the first substrate 100 isdisposed above the first substrate 100. The dispenser 520 can dispensethe emulsion 380 onto the first substrate 100 while moving from one endof the first substrate 100 to the other end thereof. As an alternative,the dispenser 520 may include, for example, a plurality of nozzles 521arranged over the entire surface of the first substrate 100 and cansimultaneously dispense the emulsion 380 over the entire surface of thefirst substrate 100.

The same quantity of hydrophobic fluid 210 should be located within eachpixel 170 of the electrowetting display device. If the display device isfor displaying a monochrome image, hydrophobic fluids 210 having, forexample, dyes or pigments of the same color are located within allpixels 170 of the display device. The emulsion 380 filled in thedispenser 520 corresponds to a fluid in which the hydrophobic fluid 210is uniformly distributed in the hydrophilic fluid 230. Therefore, whenthe emulsion 380 is dispensed onto the first substrate 100, even if thedispenser 520 is not aligned with the pixels 170 of the first substrate100, the same quantity of hydrophobic fluid 210 and the same quantity ofhydrophilic fluid 230 can be located in each pixel 170 of the firstsubstrate 100 and a uniform image may be displayed on the displaydevice.

Further, the above-mentioned scheme that does not require the alignmentmay shorten the working time in dispensing the emulsion 380 on the firstsubstrate 100. To quicken the process, the width w(E) of a droplet 381dispensed onto the first substrate 100 or the width w(D) of thedispensed emulsion 383 on the first substrate 100 may be, for example,larger than the width w(P) of the pixel 170. The width w(E) of theemulsion droplet 381 corresponds to a width of the emulsion 380 in adirection parallel to the first substrate 100 before being dropped ontothe first substrate 100 after being discharged out of the nozzle 521.The width w(D) of the dispensed emulsion 383 on the substratecorresponds to, for example, a width of the emulsion 380 in a directionparallel to the first substrate 100 after being dropped onto the firstsubstrate 100. The width w(P) of the pixel 170 may be, for example, thelargest width that can be found in an area such as for example, the areaof the pixel electrode 120 at which the emulsion 380 is to be located.For example, the width w(P) of the pixel 170 may have a value within arange from about 500 μm to about 700 μm and the width of the emulsiondroplet 381 of the emulsion 380 or the width of the dispensed emulsion383 may be larger than about 700 μm. If the emulsion droplet 381 is toolarge, an excessively large weight of the emulsion 380 may causephysical damage to the hydrophobic film 130. Therefore, the emulsiondroplet 381 should have a width which is, for example, not larger thanabout ten times of the width w(P) of the pixel 170.

After the emulsion 380 is dispensed onto the first substrate 100 and isthen separated into the hydrophobic fluid and the hydrophilic fluid, thesecond substrate (not shown) is attached to the first substrate 100. Inconsideration of this step, it may be beneficial that the dispensedemulsions 383 on the first substrate 100 are adjacent to each other andare not spaced apart from each other. Referring to FIG. 6C, to make theemulsion 380 be uniformly distributed on the first substrate 100, aportion of one dispensed emulsion 383 may be in contact with or overlapa portion of an adjacent dispensed emulsion 383. If the dispensedemulsions 383 on the first substrate 100 are small, the number of thedispensed emulsions 383 in a unit area of the first substrate 100 maybecome large and may thus require a longer time for the emulsiondispensing step as shown in FIG. 6C. The width of the dispensed emulsion383 may be, for example, at least about three times of the width w(P) ofthe pixel 170.

As an alternative, although not shown, the width of the emulsion dropletof the emulsion may be, for example, smaller than the width of onepixel. For example, the emulsion may be dispensed onto the substrate insuch a manner that emulsion droplets (minute emulsion droplets) ofseveral μm may be collected in one pixel. In this event, the width ofthe minute emulsion droplets may be, for example, narrower than thewidth of the unit pixel. The width of the unit pixel may be, forexample, the narrowest width that can be found in the area at which theemulsion is to be located. For example, the width of the minute emulsiondroplets may have a value within a range from about 1.5 μm to about 100μm and a plurality of emulsion droplets may be dispensed into one pixelby an inkjet equipment. These minute emulsion droplets are availablewhen hydrophobic fluids including dyes or pigments of different colorsare dispensed into adjacent pixels (for example, in a color displaydevice), respectively. In addition, these minute emulsion droplets mayalso be used for an electrowetting display device (for example, in amonochrome display device) in which adjacent pixels display the samecolor.

FIG. 6D is a rough sectional view of the substrate after the emulsiondispensing step as shown in FIG. 6C is completed. The emulsion 380 isfilled between the sealing members 150 located at opposite ends of thefirst substrate 100 and ultraviolet rays 531 are radiated onto theemulsion 380 from an ultraviolet ray source 530 spaced apart from theemulsion 380.

As described above, the linker 330 included in the surfactant molecule300 included in the emulsion 380 has a bond energy lower than the bondenergy of the bonds included in the hydrophobic functional groups 310and/or hydrophilic functional groups 320. Therefore, the radiation ofthe ultraviolet rays 531 onto the emulsion 380 may break the bondsincluded in the linkers 330 of the surfactant molecules 300, may reducethe quantity of the micelles included in the emulsion 380, and maychange the emulsion 380 into a separated hydrophilic fluid 233 and aseparated hydrophobic fluid 213 which are unmixable with each other aswill be described in further detail in connection with FIG. 6E. In thisevent, excessive radiation of the ultraviolet rays in view of theintensity or time of the radiation may break not only the bonds of thelinkers 330 but also the bonds of the hydrophilic 320 or hydrophobic 310functional groups. Therefore, it may be necessary to control the timeand intensity of the radiation of the ultraviolet rays 531. The abovedescription discusses radiation of the ultraviolet ray source 530 ontothe emulsion 380. However, as an alternative, to dissolve the linkers ofthe surfactant molecules 300, it is possible to apply, for example, heatto the first substrate 100 containing the emulsion 380 thereon.Otherwise, it is also possible to, for example, either simultaneouslyprovide the ultraviolet ray energy and the heat energy or provide asound wave energy, such as an ultrasonic wave to the first substrate 100containing the elmusion 380 thereon.

FIG. 6D shows a state in which the ultraviolet rays 531 are radiatedonto the first substrate 100 on which the second substrate (not shown)is not assembled. However, for example, as an alternative, after thefirst substrate 100 and the second substrate are attached to each other,the ultraviolet rays 531 may be radiated toward the attached firstsubstrate 100 and second substrate from the outside of the attachedfirst substrate 100 and second substrate. For example, after the firstsubstrate 100 on which the emulsion 380 has been dispensed is attachedto the second substrate, the ultraviolet rays 531 may be radiated fromabove the second substrate. As an alternative, for example, after thefirst substrate 100 and the second substrate are attached to each other,an emulsion may be injected into the space between the attached firstsubstrate 100 and second substrate through a corner of the attachedfirst substrate 100 and second substrates by a proper method, such as,for example, a vacuum injection, and the ultraviolet rays 531 may bethen radiated from above the second substrate.

FIG. 6E is a rough sectional view of the first substrate 100 in whichthe emulsion 380 has been separated into a separated hydrophobic fluid213 and a separated hydrophilic fluid 233 by the ultraviolet rayradiating step shown in FIG. 6D. The separated hydrophobic fluid 213includes the hydrophobic functional groups 310 of the surfactantmolecules 300 mixed with molecules of the original hydrophobic fluid210, and the separated hydrophilic fluid 233 includes the hydrophilicfunctional groups 320 of the surfactant molecules 300 mixed withmolecules of the original hydrophilic fluid 230. The separatedhydrophobic fluid 213 and the separated hydrophilic fluid 233 do not mixwith each other.

When a linker 330 of a surfactant molecule 300 has an S—S bond, thehydrophobic 310 and hydrophilic 320 functional groups of the surfactantmolecules 300 may be changed to thiol molecules. Therefore, at least oneof the separated hydrophobic fluid 213 and the separated hydrophilicfluid 233 as shown in FIG. 6E may include thiol molecules. As analternative, for example, a linker 330 of a surfactant molecule 300 mayhave a bond having a bond energy lower than the bond energy of the C—Cor C—O bond wherein the bond of the linker 330 may be a bond includingone of Si—C, C—P, N—Si, N—S, O—S, or S—P, which may be broken byultraviolet rays, heat, or catalyst. In this alternative, the separatedhydrophilic fluid 233 or the separated hydrophobic fluid 213 mayinclude, for example, an element included in the bond of the linker 330of the surfactant molecule 300 broken by ultraviolet rays, heat, orcatalyst as described above.

FIG. 6F is a sectional view of an electrowetting display device 10 inwhich the second substrate 190 has been attached to the first substrate100 as shown in FIG. 6E. The second substrate 190 is attached to, forexample, the sealing members 150 disposed at the edges of the firstsubstrate 100 and prevents the separated hydrophobic and hydrophilicfluids 213 and 233 from leaking out of the display device 10. The secondsubstrate 190 may be, for example, a flexible substrate or a rigidsubstrate. For example, the second substrate 190 may include flexiblesubstrates made of glass, plastic, or a glass fiber reinforced plastic(FRP).

In the present exemplary embodiment, the sealing members 150 are formedon the first substrate 100 prior to attaching the second substrate 190to the first substrate 100 but exemplary embodiments of the presentinvention are not limited thereto. For example, alternatively, in anexemplary embodiment, the sealing members 150 may be disposed on edgesof the second substrate 190 and then the second substrate 190 havingsealing members formed thereon may be attached to the first substrate100 and the emulsion 380 is then formed between the attached first andsecond substrates 100, 190.

Having described exemplary embodiments of the present invention, it isfurther noted that it is readily apparent to those of ordinary skill inthe art that various modifications may be made without departing fromthe spirit and scope of the invention which is defined by the metes andbounds of the appended claims.

What is claimed is:
 1. An electrowetting display device comprising: afirst substrate; a pixel electrode disposed on the first substrate; ahydrophobic film disposed on the pixel electrode; a hydrophobic fluiddisposed on an area of the hydrophobic film, wherein the hydrophobicfluid is configured to move on the hydrophobic film in response to avoltage applied to the pixel electrode; a hydrophilic fluid disposed onthe hydrophobic fluid; and a second substrate disposed on thehydrophilic fluid and spaced apart from the hydrophobic film, whereinthe hydrophobic fluid comprises molecules including hydrophobicfunctional groups of a cleavable surfactant and wherein the hydrophilicfluid comprises molecules including hydrophilic functional groups of thecleavable surfactant.
 2. The electrowetting display device of claim 1,wherein at least one of the hydrophobic fluid or the hydrophilic fluidcomprises thiol molecules.
 3. The electrowetting display device of claim1, wherein the hydrophobic fluid comprises a saturated hydrocarbonhaving at least ten carbon atoms, wherein the hydrophilic fluidcomprises ethylene glycol and glycerin, wherein the hydrophobicfunctional group is a functional group of a hydrocarbon having at leastten carbon atoms, and wherein the hydrophilic functional group comprisesa functional group including an ether bond.
 4. A method of manufacturingan electrowetting display device, comprising: providing a firstsubstrate including a base substrate having a plurality of pixelelectrodes formed on the base substrate, a hydrophobic film formed onthe plurality of pixel electrodes, and at least one sealing memberdisposed at an edge of the first substrate; mixing a hydrophobic fluid,a hydrophilic fluid, and a cleavable surfactant with each other to forman emulsion, wherein the cleavable surfactant includes a hydrophobicfunctional group, a hydrophilic functional group and a linker disposedbetween the hydrophobic functional group and the hydrophilic functionalgroup, wherein the linker is connected to the hydrophobic functionalgroup and the hydrophilic functional group and wherein the linker has acleavable bond; applying the emulsion on the first substrate; applyingat least one of ultraviolet rays or heat on the emulsion applied on thefirst substrate to separate the hydrophobic fluid and the hydrophilicfluid from each other; and disposing a second substrate on the at leastone sealing member of the first substrate.
 5. The method of claim 4,wherein a substantially identical amount of hydrophobic fluid isdistributed in each of the pixel electrodes.
 6. The method of claim 4,wherein a width of a pixel disposed on the first substrate in an area inwhich the emulsion is disposed is greater than a width of a pixeldisposed on another area of the first substrate in which the emulsion isnot disposed, wherein the emulsion is dispensed onto the first substratethrough a nozzle of a dispenser as a droplet, wherein the emulsiondroplet has a width in a direction parallel to the first substratebefore the emulsion droplet is dropped onto the first substrate afterbeing discharged out of the nozzle, and wherein the width of at leastone of the pixels disposed on the first substrate is smaller than thewidth of the emulsion droplet.
 7. The method of claim 6, wherein theemulsion droplet is dispensed on the first substrate and becomes adispensed emulsion and wherein the dispensed emulsion has a widthgreater than the width of at least one of the pixels disposed on thefirst substrate.
 8. The method of claim 7, wherein the width of thedispensed emulsion is not larger than about ten times of the width of atleast one of the pixels disposed on the first substrate.
 9. The methodof claim 4, wherein the emulsion is dispensed onto the first substrateafter becoming an emulsion droplet formed by a nozzle of the dispenser,the emulsion droplet becomes a dispensed emulsion when the emulsiondroplet has been dispensed onto the first substrate, and wherein onedispensed emulsion overlaps an adjacent dispensed emulsion.
 10. Themethod of claim 4, wherein the emulsion is formed by mixing thehydrophobic fluid, the hydrophilic fluid, and the cleavable surfactantwithin a container.
 11. The method of claim 4, wherein the at least oneof the ultraviolet rays or the heat applied on the emulsion has anintensity capable of breaking the cleavable bond earlier than bonds ofthe hydrophilic functional group and the hydrophobic functional group.12. The method of claim 11, wherein the cleavable bond of the linker ofthe cleavable surfactant is broken by applying the at least one of theultraviolet rays or heat to the emulsion which in turn causes thehydrophobic fluid and the hydrophilic fluid to separate from each other,wherein the separated hydrophobic fluid comprises molecules includingthe hydrophobic functional group and a first portion of the brokencleavable bond of the linker of the cleavable surfactant and wherein theseparated hydrophilic fluid comprises molecules including thehydrophilic functional group and a second portion of the brokencleavable bond of the linker of the cleavable surfactant.
 13. The methodof claim 12, wherein the cleavable bond of the cleavable surfactant is abond selected from the group consisting of carbon-silicon (C—Si),carbon-phosphor (C—P), nitrogen-silicon (N—Si), nitrogen-sulfur (N—S),oxygen-oxygen (O—O), oxygen-sulfur (O—S), sulfur-phosphor (S—P),sulfur-sulfur (S—S), and combinations thereof.
 14. The method of claim13, wherein the cleavable bond is a sulfur-sulfur (S—S) bond and thehydrophobic fluid or the hydrophilic fluid comprises thiol molecules.15. The method of claim 4, wherein the hydrophobic functional group andthe hydrophilic function group include one of a carbon-carbon bond or acarbon-oxygen bond, wherein the cleavable bond has a bond energy lowerthan a bond energy of the carbon-carbon bond or a bond energy of thecarbon-oxygen bond included in the hydrophobic functional group and thehydrophilic functional group, and wherein the cleavable bond isconfigured to be broken by absorbing an energy no less than the bondingenergy of the carbon-carbon bond or the bonding energy of thecarbon-oxygen bond.
 16. The method of claim 15, wherein the bond energyof the cleavable bond is no greater than about 600 kJ/mol.
 17. Themethod of claim 4, wherein the cleavable bond includes a bond selectedfrom the group consisting of carbon-silicon (C—Si), carbon-phosphor(C—P), nitrogen-silicon (N—Si), nitrogen-sulfur (N—S), oxygen-oxygen(O—O), oxygen-sulfur (O—S), sulfur-phosphor (S—P), sulfur-sulfur (S—S),and combinations thereof.
 18. A method of manufacturing anelectrowetting display device, comprising: providing a first substrateincluding a base substrate having a plurality of pixel electrodes formedon the base substrate and a hydrophobic film formed on the plurality ofpixel electrodes; mixing a hydrophobic fluid, a hydrophilic fluid, and asurfactant having a linker with each other to form an emulsion includinga micelle in which a hydrophobic functional group of the surfactant isbonded to a molecule of the hydrophobic fluid, a hydrophilic functionalgroup of the surfactant is bonded to a hydrophilic molecule of thehydrophilic fluid, and the linker of the surfactant has a cleavable bondthat interconnects the hydrophobic functional group and the hydrophilicfunctional group to each other, wherein the hydrophobic functional groupand the hydrophilic functional group include at least one of acarbon-carbon bond or a carbon-oxygen bond, and wherein the cleavablebond has a bond energy lower than a bond energy of the at least one of acarbon-carbon bond or a carbon-oxygen bond included in the hydrophobicfunctional group and the hydrophilic functional group; applying theemulsion on the first substrate; applying a form of energy to theemulsion to break the cleavable bond of the linker of the surfactant andto separate the hydrophobic fluid and the hydrophilic fluid from eachother such that the separated hydrophobic fluid and the separatedhydrophilic fluid are unmixable with each other; and disposing a secondsubstrate on the first substrate.
 19. The method of claim 18, whereinthe form of energy applied to the emulsion to break the cleavable bondof the surfactant comprises at least one of ultraviolet ray energy, heatenergy or sound wave energy.
 20. The method of claim 18, wherein thehydrophobic fluid and the hydrophilic fluid are mixed in a ratio ofabout 1:9 in forming the emulsion.
 21. The method of claim 18, whereinthe hydrophobic functional group has a structure substantially similarto a structure of the hydrophobic molecule of the hydrophobic fluid andwherein the hydrophilic functional group has a structure substantiallysimilar to a structure of the hydrophilic molecule of the hydrophilicfluid.
 22. The method of claim 21, wherein the hydrophobic functionalgroup and the hydrophobic molecule of the hydrophobic fluid each includea decane molecule and wherein the hydrophilic functional group and thehydrophilic molecule of the hydrophilic fluid each include an ethyleneglycol molecule.
 23. The method of claim 21, wherein the hydrophobicfunctional group and the hydrophobic molecule of the hydrophobic fluideach include an alkane molecule and wherein the hydrophilic functionalgroup and the hydrophilic molecule of the hydrophilic fluid each includea glycerol molecule.
 24. The method of claim 18, wherein the cleavablebond of the linker of the cleavable surfactant is broken by applyingultraviolet rays to the emulsion which in turn causes the hydrophobicfluid and the hydrophilic fluid to separate from each other, wherein theseparated hydrophobic fluid comprises molecules including thehydrophobic functional group and a first portion of the broken cleavablebond of the linker of the surfactant and wherein the separatedhydrophilic fluid comprises molecules including the hydrophilicfunctional group and a second portion of the broken cleavable bond ofthe linker of the surfactant.
 25. A method comprising: mixing ahydrophobic fluid, a hydrophilic fluid and a surfactant to form anemulsion, wherein the surfactant includes a hydrophobic group, ahydrophilic group and a linker with a cleavable bond; applying theemulsion on a substrate having a pixel electrode; and applying at leastone of ultraviolet rays or heat to the emulsion to separate thehydrophobic fluid and the hydrophilic fluid from each other.
 26. Themethod of claim 25, further comprising applying a voltage to the pixelelectrode.
 27. The method of claim 25, wherein the emulsion includes nogreater than about 15% by weight of the surfactant.
 28. The method ofclaim 25, wherein the at least one of ultraviolet rays or heat areapplied to the emulsion for no greater than about 15 minutes.
 29. Themethod of claim 25, wherein applying the emulsion to the substrateincludes dispensing a droplet of the emulsion onto the substrate. 30.The method of claim 29, wherein a width of the droplet is greater than awidth of the pixel electrode.
 31. The method of claim 30, wherein thewidth of the pixel electrode is included in a range of about 500micrometers to about 700 micrometers and the width of the droplet isgreater than about 700 micrometers.
 32. The method of claim 30, whereinthe width of the droplet is about three times greater than the width ofthe pixel electrode.
 33. The method of claim 29, wherein a width of thedroplet is less than a width of the pixel electrode.
 34. The method ofclaim 33, wherein the width of the pixel electrode is included in arange of about 1.5 micrometers to about 100 micrometers.
 35. The methodof claim 33, wherein applying the emulsion on the substrate includesdispensing a plurality of droplets into the pixel electrode.
 36. Themethod of claim 25, further comprising producing an electrowettingdisplay device by attaching the substrate to an additional substrate,and wherein the at least one of ultraviolet rays or heat are appliedafter attaching the substrate to the additional substrate.